Hoist



Feb. 28, 1939. E B GRUBER 2,148,616

HOIST Filed May 15, 1937 -INVENT OR.

ATIORNEY Patented Feb. 28, 1939 UNITED STATES PATENT OFFICE,

HOIST Earl B. Gruber, West Allis, Wis., minor to The Hell 00., Milwaukee, Win, a corporation of Wil cousin Application my 15, 1937, Serial No. 142,185

3 Claims.

My present invention relates in general to improvements in hoists, and relates more specifically to improvements in the construction and operation of fluid pressure actuated hoisting mechatransporting material in bulk, to utilize so-called dump trucks each having a tiltable body adapted to be elevated or swung into dumping position 15 with the aid of one or more hydraulic hoists. The

type of hydraulic hoist or jack ordinarily employed for this service, comprises a cylinder pivotally suspended from the chassis oi the transporting vehicle, and a piston slidable within the 20 cylinder and having a rod pivotally attached to a swinging portion of the body; the cylinder being supplied'with fluid, such as oil under pressure, by'means of a pump which is operable from the. propelling motor of the vehicle. Due to the fact that these trucks are usually provided with a conglomeration of other equipment such as wheel driving mechanism, it is necessary to make the hoists as compact as possible in order to retain the center of gravity of the dump body desirably lcw while avoiding interference with the truck equipment and dump body. It is also well known, that maximum force is required to start the loaded dump body during tilting or hoisting 35 thereof, and that the fluid pressure in the hoists diminishes rapidly as the body approaches its uppermost position. The hoists must however be of sufficient size and capacity to meet the starting requirements, and this fact makes it necessary 40 under the prior practice to provide hoisting cylinders having relatively large diameter throughout their lengths so that the upper ends thereof make it diiilcult to produce a desirably compact assemblage without interference or obstruction.

My present invention therefore contemplates provision of a new and useful hydraulic hoist assemblage wherein the starting power is greater than that required during the subsequent piston 50 stroke, and which is extremely compact as compared to other hoists of like capacity.

Another specific object of the invention is to provide improved fluid pressure actuated hoist structure which is especially adapted for use in 55 conjunction with vehicular dump bodies where limited space for the installation hoisting equipment is available.

A further specific object oi. my invention is the provision of an improved starting appliance for hydraulic hoists, which while greatly aug- 5 menting the starting pressure available,does not, interfere with the normal operation of the motion transmitting member or piston oi the hoist.

Still another specific object of the invention is to provide a starting plunger which is cooperable with a motion transmitting piston of a hoist in such a way, that after the starting force has been applied, the piston will automatically leave the zone of action of the plunger and may proceed for the remainder of its stroke in a normal manner.

An additional specific object oi. my invention is to provide an improved hoisting appliance which is conveniently applicable to fluid pressure hoists of various types, and which may be manufactured at moderate cost.

These and other objects and advantages of my present invention will be apparent from the following detailed description.

A clear conceptlon of one embodiment of my invention, and of the mode of constructing and of utilizing hydraulic hoists built in accordance with the improvement, may be had by referring to the drawing accompanying and forming a part of this specification wherein like reference char- 0 acters designate the same or similar parts in the several views.

Fig. 1 is a fragmentary side view of a typical vehicular dump body hydraulic hoist installation, showing the dump body lowered in solid lines, and elevated or tilted in dot-and-dash lines;

Fig. 2 is an enlarged central longitudinal section through one of my improved hoists, showing the starting plunger and piston thereof in lowermost position; and

Fig. 3 is a similar view of the hoist, showing the plunger and piston in extreme elevated position.

' While I have shown the invention by way of illustration, as being applied to a single cylinder, single acting, trunnion suspended hydraulic hoist especially adapted for cooperation with a tiltable dump truck body, it is not the intent to thereby unnecessarily restrict the scope, since the im-, provement is obviously more generally applicable to other types of hoists or jacks otherwise suspended.

Referring to the drawing, the assemblage shown in Fig. 1 comprises in general a vehicle having a chassis 5 ordinarily supported upon rear 56 movable in the cylinder and provided with a rod l2 the outer end of which is pivotally attached to the body by a pin |3. All of these elements are of well known construction, and while the hoist herein shown is of the single cylinder, single acting type similar to that shown in the prior, Hell and Eisenberg Patent No. 1,798,469, granted March 31, 1931, this hoist may be of the well known double-acting type. or of the telescopic piston type, or of the twin cylinder type.

My present improved hoist with the new start ing appliance associated therewith, is shown somewhat diagrammatically in Figs. 2 and 3, and in this showing, some of the fluid conducting ports and passages have been displaced or thrown into the planes of the sections in order to clarify the disclosure This hoist has a relatively largebut short cylindrical bore H in the lower portion of the cylinder 9 near the trunnions l0, and has a concentric smaller cylindrical bore l of greater length above the bore |4,

the piston being slidable only within the uppersmall bore l5. The piston rod I2 is rigidly secured to the piston II and projects through a stuifing box carried by the upper end bead l8, and a startingplunger H is slidable' within the lower enlarged bore l4 and has a stem l8 adapted to abut against the lower face of the piston II, the stem |8 being guided at its abutment end within the small bore l5 by means of a spider ring I9. The piston rod |2 directly above the piston I] is embraced by a helical spiral compression spring 20 which is adapted to engage the upper end head "5 when the piston is fully elevated, and the lower extremity of the cylinder 8 beneath the plunger I1 is enclosed by a lower end head 2| to which a gear pump 22 is attached. This pump 22 is swingable' with the hoist, and is adapted to be driven from the vehicle propelling motor through universal joints and a driving shaft 23, in a well-known manner.

The lower end' head 2| is provided with a nonreturn pump discharge valve 24 and with a port 25 which connects this valve with the lower end of the cylinder bore |4 beneath the plunger H. The end head 2| is also provided with a through port 26 one end of which communicates with the suction side of the pump 22, and the opposite end of which is in open communication with a passage 21 formed in the wall of the cylinder 9 and leading into the upper portion of the bore IS. A rotary control valve 28 is mounted in the lower head 2| between the ports 25, 26 and is operable by linkage 29 to either connect these ports as shown in Fig. 2, or to close oif communication therebetween as shown in Fig. 3. The medial portion of the cylinder passage 21 is communicable with the upper end of the bore |4 through a port 30, and the extreme upper end of the passage 21 is connected by a port 3| with the space above the piston H at all times,'the port 3| having a non-return check valve 32 therein. The medial portion of the large bore I4 is moreover connected with the lower end of During normal use of the dump truck, the body I will be in lowered or horizontal position as shown in full lines in Fig. 1, and the control valve 28 will be positioned as shown in Fig. 2, so that the ports 25, 26 will be directly connected. The pump 22 is normally idle, but if this pump is placed in operation and the control valve 28 remains in the position shown in Fig. 2, liquid will merely be circulated from the port 26 through the pump, past the discharge valve 24 and through the port 25 and valve 28 to the suction port 26. If the valve 28 is subsequently adjusted by manipulation of the linkage 29 to position the same as shown in Fig. 3, communication between the ports 25, 28 is out OK and the liquid will thereafter be drawn by the pump from the space within the bore l5 above the piston through the passage 21 and port 26, and will be delivered past the valve 24 and through the port 25 into the lower bore H beneath the plunger H. The liquid under pres- 'sure acting upon the lower face of the plunger 'will cause this plunger to move upwardly, thereby simultaneously moving the piston upwardly by virtue of the contact between the stem l8 and the. lower face of the piston. The rod l2 will then be urged forwardly under the influence of the pressure acting upon the relatively large lower face of the plunger I1, and this action will continue until the plunger moves beyond the lower end of the passage 33. The liquid under pressure will then escape through the passage 33 and will act directly upon the lower face of the smaller piston H, and will continue to elevate this piston II and its rod l2 until the body 1 has been fully tilted as indicated in the dot-and-dash lines in Fig. 1. The pump 22 will then continue to create fluid pressure within the lower chambers of the bores l5, I4, and the spring 20 will be compressed as shown -in Fig. 3, thus maintaining the body 1 in tilted piston II and plunger H, the piston II will displaceliquid from within the bore I5 above this piston, and the plunger I! will likewise displace liquid from within the bore l4 above the plunger through the port 30, but the displacement of liquid by the plunger will continue only until the lower edge thereof uncovers the passage 33.

In order to lower the body 1, his only necessarytorestore the control valve 28 to the position shown in 2. The spring 2|] will then become efiective to initially move the piston away from the upper head I6, and liquid from within the passage 21 will flow through the port 3| and past the valve 32 into the space within the bore |5 above the piston. As soon as the piston II has uncovered the upper end of the passage 21 where this passage communicates directly with the bore IS, the weightof the body and of the piston II and rod l2 will cause these elements to drop'by gravity and will also cause the piston II" to ultimately return the plunger ll to the position shown in Fig. 2. The passage 33 will then be connected through the displacement chamber above the plunger I1 and through the port 3|] with the suction passage 21 and suction port 26 of the pump, and it will be noted that the displacement chamber above the piston merely serves as a liquid storage res- .ervoir for supplying the pump 22 with liquid. The liquid-normally utilized in systems of this type is oil, and this oil besides constituting the actuating fluid, also maintains the working well lubricated.

Due to the fact that the lower face of the plunger I1 is of considerably greater area than the lower face of the piston Ii, it must be apparent that the pressure initially applied to this plunger I! to move the piston II will be much greater than if this same unit pressure were applied to the piston direct. After the starting load has been taken care of by the enlarged plunger H, the inertia of the body 1 and its load combined with the release of material from the body, will materially decrease the pressure necessary in order to efiect further tilting of the body I. This subsequent movement of the body can therefore be readily taken care of by the smaller piston H. While the ideal condition in a hoist of this type would be the provision of a conical gradually decreasing bore with a piston adapted to gradually diminish in diameter and coacting with this conical bore, such a structure would be difllcult to construct. Substantially the same action may, however, be secured by providing a series of plungers ll of gradually diminishing diameter and coacting in series with the piston l I, the successive plungers being released as the requisite lifting force diminishes. In the case of a simple hoist such as shown in the present application, only one of these booster plungers I! would be necessary, but in longer hoisting units a series such as hereinabove referred to may be desirable.

From the foregoing detailed description it will be apparent that my invention provides simple, compact and highly efficient mechanism for effecting quick starting of a fluid pressure actuated hoist, while permitting normal functioning of the hoist after suflicient starting momentum has been created. The accessory may be formed integral with or separable from an ordinary hoist, and the parts plunger I! after having served its function is tem to a minimum, thereby reducing the danger of leakage, and augmenting the safety. The improved assemblage is obviously simple and compact in construction and may be readily manufactured at moderate cost, and the invention has actually demonstrated its superiority in starting a hoist of this type while permitting reduction in the cylinder diameter to a minimum.

It should be understood ,that it is not desired slidably coacting with both of said bores and said piston being initially movable by said plunger until the latter has reached the end of its stroke and being thereafter movable away from said plunger, a fluid conducting passage connecting the medial portion of one of said bores with the adjacent end of the other bore, means for admitting fluid under pressure into one of said bores and through said passage into the other, and a port for effecting free escape of fluid from the space between said plunger and piston when said piston is being initially moved by said plunger, said port being closed by said' plunger when said plunger reaches the end of its stroke remote from said fluid admission means.

2. In a hoist, a cylinder having small and large alined bores in open end communication with each other, a piston slidable directly within said small bore, a plunger slidable directly within said large bore and having a guiding portion slidable directly within said small bore and adapted to abut the adjacent end of said piston, a fluid pressure passage connecting an intermediate portion of said large bore with the adjacent end of said small bore, means for introducing fluid under pressure into said large bore remote from said small bore, and a port adapted to effect free escape of fluid from the space between said plunger and piston when said piston is being initially moved by said plunger, said port being adapted to be closed by said plunger when said plunger reaches the end of its stroke remote from said fluid admission means.

3. In a hoist,,a cylinder having small and large bores, a piston slidable in said small bore, a plunger slidable in said large bore and having a portion directly engageable with said piston to initially move the latter, a liquid conducting passage connecting the medial portion of said large bore with the adjacent end of said small bore, means for admitting liquid under pressure into the end of said large bore remote from said small bore, and means for effecting free escape of liquid from the space between said plunger and piston when said piston is being initially moved by said plunger, said plunger being formed to close said escape means when disposed at the end of its stroke remote from said liquid admission means.

EARL B. GRUBER. 

